Heretofore wellbores have been drilled into the earth's surface to penetrate one or more geologic formations containing a liquid mineral such as crude oil for recovery at the earth's surface. When the pressure in the producing geologic formation is not sufficient to force the liquid mineral to the earth's surface, artificial lifting, i.e., pumping, is employed to move the liquid from the producing formation or formations through the wellbore to the earth's surface for recovery, transportation, processing, and the like.
One form of artificial lift widely employed in the oil patch is a reciprocating pumping unit sometimes referred to as a pump jack which is connected by a string of sucker rods to a pump that is disposed downhole in the wellbore in the vicinity of the geologic formation from which the desirable liquid is to be pumped. The pumping unit is a complete set of surface equipment necessary to impart up-and-down (reciprocating) motion to the sucker-rod string and the downhole pump. This equipment includes a prime mover or power plant connected by way of a pitman to a walking beam at one end of which is a horsehead. The sucker-rod string is connected to the horsehead and as the horsehead reciprocates up and down it moves the sucker-rod string and the downhole pump with it.
Wellbores are completed at the earth's surface with a wellhead which closes off the one or more casing and tubing strings that are disposed in the wellbore. The sucker-rod string passes through the wellhead and exits from the wellhead at the top thereof through a device known as a stuffing box. The stuffing box contains a packing for keeping produced liquid from leaking out around the sucker rod as it exits the wellhead and thereafter running down the outside of the wellhead to the earth's surface to contaminate same. Liquid produced from the wellbore into the wellhead is transferred by way of a conduit means connected between a tee in the wellhead and a tank battery for storage, treatment, and subsequent transportation.
Speed reduction between the power plant and the pitman is accomplished by combination of V-belt drive and/or gear reducer means well known in the art so that with an engine speed of, for example, 600 revolutions per minute, a speed reduction ratio of 30 to 1 can be accomplished to cause the unit to operate at 20 strokes per minute. With one end of the pitman connected to the speed reduction means and the other end to the walking beam, the rotational motion generated by the power plant is translated into the reciprocating motion of the walking beam, horsehead, sucker-rod string and downhole pump. The power plant may be either an internal combustion engine or electric motor or the like. A set of weights attached to the walking beam counter-balances the weight of the sucker rods and part of the weight of the liquid being pumped, and helps the power plant lift the sucker rods and liquid on the upstroke.
This type of pumping system needs a means for packing or sealing off the pressure inside the wellbore where the sucker-rod string exits from the wellhead to prevent leakage of liquid and gas from inside the wellhead at that point. Stuffing boxes consist of flexible material or packing housed in a box which provides a means for compressing the packing around a sucker rod section, often times a polished rod. The stuffing-box packing is replaced by a field hand when it becomes worn and loses its seal thereby allowing small amounts of liquid and/or gas to leak out of the wellhead before the packing is replaced.
This invention is directed to catching liquid and/or gas leaking from the wellhead, particularly the stuffing box, to prevent such fluids from contaminating the earth around the wellhead and collecting such leaking fluids in a manner so that they can be returned to the wellbore by way of the wellhead and/or disposed of in other manners such as in a nearby tank battery, portable collection tank, or the like.